Static material mixers are well known as a means for mixing a plurality of materials into a single mass without a need for a rotary mixer, such as a motor. See for example Federighi et al, U.S. Pat. No. 4,511,258 entitled "Static Material Mixing Apparatus". However when mixing liquids which contain solids, such prior art static material mixers are prone to clogging when the solids pass through. This clogging requires repeated maintenance which is expensive and can be quite distasteful, such as when the static material mixer is utilized to mix raw sewage.
The invention is provided to eliminate some or all of the above problems.